Player leaves court

[Vinski]

Was watching a GV playoff game the other evening and came across an unusual situation. A1 commits a foul on B1 and gets called for it. This leaves A1 visibly unhappy with the call. It was a bonus situation, so as the players where lining up for the free throws, A1 simply walks off the floor and sits down at the bench. No subs or anything. The officials saw this and actually appeared to be giving her a little extra time to get back on the floor before the ball was administer to the free-throw shoot. As soon as the ball was given to the shooter, the trail immediately signaled the technical foul.
Now, I can’t seem to find in the rule book exactly what went down here (I’m a rookie so can’t find things quickly yet). But was the T for leaving the court, or unsporting moping or for the coach not having 5 players on the court or something else. Also, if she would have returned before the ball was administered to the shooter would all have been well? Thanks.